Delphi: XML data binding (coding)

I need to generate an XML file, and I have its schema in XSD format.

I created classes using the XML Data Binding Wizard, but:

One of the requirements is that xml has an encoding tag set to "utf-8".

I did this before creating the xml directly using the IXMLDocument, doing the following:

var xml:IXMLDocument;
.
.
xml.Encoding:='utf-8';

The first line of XML becomes <? xml version = "1.0" encoding = "utf-8"? >

But now, with the data binding wizard, I tried something similar:

var xml:IXMLAuditFile;
.
.
xml.OwnerDocument.Encoding:='utf-8';

But this encoding does not appear in the xml file: <? xml version = "1.0"? >

Is there any other place where I should set the encoding when using XML data binding?

Thank. Oh well